Urolithins are metabolites produced by the action of mammalian, including human, gut microbiota on ellagitannins and ellagic acid. Ellagitannins and ellagic acid are compounds commonly found in foods such as pomegranates, nuts and berries. Ellagitannins are minimally absorbed in the gut themselves. Urolithins are a class of compounds with the representative structures below and they have been shown to have potent effects on the improvement of a number of health conditions.

where A, B, C, D, W, X, Y and Z are each independently selected from H or OH, and at least one of them is OH.
In particular, the compounds Urolithin A and Urolithin B have been shown to be highly biologically active in vitro and in vivo.

Urolithins have been proposed as treatments of a variety of conditions related to inadequate mitochondrial activity, including obesity, reduced metabolic rate, metabolic syndrome, diabetes mellitus, cardiovascular disease, hyperlipidemia, neurodegenerative diseases, cognitive disorder, mood disorder, stress, and anxiety disorder; for weight management, or to increase muscle performance or mental performance. See WO2012/088519 (Amazentis SA). In WO2007/127263 (The Regents of the University of California), the use of urolithins for the treatment of various neoplastic diseases is described.
International patent publication no. WO2014/004902 (derived from application PCT/US2013/48310) discloses a method of increasing autophagy, including specifically mitophagy, in a cell, comprising contacting a cell with an effective amount of a urolithin or a pharmaceutically acceptable salt thereof, thereby increasing autophagy, including specifically mitophagy, in the cell. Administration may be to a subject having a disease or condition selected from metabolic stress, cardiovascular disease, endothelial cell dysfunction, sarcopenia, muscle degenerative disease, Duchenne muscular dystrophy, alcoholic liver disease, nonalcoholic fatty liver disease, drug-induced liver injury, α1-antitrypsin deficiency, ischemia/reperfusion injury, inflammation, aging of the skin, inflammatory bowel disease, Crohn's disease, obesity, metabolic syndrome, type II diabetes mellitus, hyperlipidemia, osteoarthritis, neurodegenerative disease, Alzheimer's disease, Huntington's disease, Parkinson's disease, amyotrophic lateral sclerosis, age-related macular degeneration, mitochondrial diseases (including for example poor growth, loss of muscle coordination, muscle weakness, visual problems, hearing problems, heart disease, liver disease, kidney disease, gastrointestinal disorders, respiratory disorders, neurological problems, autonomic dysfunction sometimes learning disabilities, and dementia as a result of mitochondrial disease), muscle diseases; sporadic inclusion body myositis (sIBM), cancer, cognitive disorder, stress, and mood disorder.
Whilst urolithin compounds are known to possess properties that render them useful in a variety of therapies, they are highly water-insoluble. Consequently, formulation of urolithins into aqueous formulations is not straightforward. There thus remains a need for compositions of urolithins that are sufficiently soluble to allow for ready administration, to provide urolithin that is safe and active in the desired therapeutic use.